Current automobiles are required to meet stringent emissions standards. These standards include both federal regulations (U.S. and foreign) and state specific regulations (i.e., California Air Resources Board (CARB)). The emissions standards not only set maximum emissions levels, but also require that vehicles containing onboard diagnostics (OBD) are capable of determining catalyst performance. In particular, the diagnostic system must be able to identify a catalyst that has degraded to the point of no longer providing effective removal of harmful emissions.
The traditional approach to detecting failed catalysts requires the addition of ceria, or other materials with high oxygen storage rates, to the catalysts. The high oxygen storage exhibited by these catalysts makes it possible to simply compare the oxygen level downstream from the catalyst to the oxygen level upstream from the catalyst to determine if the catalyst is performing correctly. An increase in downstream oxygen levels indicates a decrease in catalyst oxygen storage, which correlates to catalyst degradation and decreased performance. Zero ceria catalyst or catalysts with little or no oxygen storage present difficulties in determining catalyst degradation and performance. Therefore improvement in the art is desirable.